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MG MGB Technical - Throttle shaft bushing mistery

I took my HIF4carb bodies to the machine shop and had them tap out the old bushings.The old bushings appear to be split steel and are about 1/2 inch long with the markings DGY on them of course the new bushings from Moss are one piece Bronze and are 3/4 of an inch long. The old bushings seem to fit tighter than the new ones on the new shafts .Which should I use? Has anyone come across this before? I don't know the history of the carbs but did notice someone had changed the standard needle and jet to the Grose-jet.

Thanks

Ben
Ben Stone

Ben - Someone before you probably had the original bushings replaced with teflon bushings from Burlen Fuel Systems. These bushings were a split steel cylinder with a teflon lining on them. Cheers - Dave
David DuBois

From the work I have done on HIF carbs I would say the split bush Burlen sell is broadly the same as the original. All bushes I have taken out have been split steel cylinders.

The split steel bush is shorter than the hole. You need to take care to bush it in so that it is flush with the inside of the carb not with the outside. Otherwise you will never get the idle speed set correctly.
David Witham

The trick to rebushing is to jig your reamers so as to not penetrate all the way through the body, only remove just enough to provide a seat for the new bushing. A lot of time the old bushing will come out (break loose) as you ream. I leave the parent material intact next to the throttle disk. Of course, this means you need to provide perfect alignment from one side to the other. The final instllation then needs to be reamed to final ID.

warmly,
dave
Dave Braun

Ben- I believe the wobble range on the shaft is 1-10 k. We've found closer to 1 provides a steady idle. All the old bush ID I've seen look like eggs. I've had Grosse jets stick open on floatsum between the ball and seat, so have gone back to the old cone rubbers. The HIF seem to be a better mousetrap than the HS, so with proper new bush and spindle, you should be good to go on the road again.Vic
vem myers

This thread was discussed between 28/11/2011 and 01/12/2011

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